The present invention relates to a high velocity gun propellant.
A gun propellant is a chemical substance capable of reacting rapidly to produce a hot gas. When confined in the chamber and bore of a gun the hot gas generated by the propellant exerts a pressure on the base of the projectile accelerating it to a high velocity.
For a gun of fixed pressure rating and barrel length there is a characteristic velocity obtainable with a given projectile weight. For a heavy projectile the velocity is limited by the design pressure of the gun barrel and the total amount of energy and gas available from the propellant. For light projectiles the velocity is limited by the velocity that the propellant gas can follow the projectile down the bore continuing to apply pressure to its base.
The velocity with which the propellant gas can flow after the projectile and continue to accelerate it is determined by the speed of sound in the gas, i.e., the sonic velocity. The sonic velocity (V) of a gas is given by equation (1): ##EQU1## where .tau.=the ratio of the gas specific heat at constant pressure (c.sub.p) to the gas specific heat at constant volume (c.sub.v), R=the universal gas constant 8.314.times.10.sup.7 gram cm.sup.2 /sec.sup.2 .degree. K. mole, T=temperature in degrees Kelvin (.degree. K.) and m=the gram molecular weight of the gas. This expression indicates that the gas with high temperature (T) and low molecular weight would have the highest sonic velocity. Table 1 displays the sonic velocity for several gases at 2500.degree. K.
TABLE 1 ______________________________________ Theoretical Sonic Velocity of Gases at 2500.degree. Kelvin Molecular Weight Sonic Velocity Gas .tau. grams/mole m/sec ______________________________________ Nitrogen 1.40 28 1019 Carbon Dioxide 1.23 44 762 Carbon Monoxide 1.29 28 978 Water Vapor 1.21 18 1182 Helium 1.66 4 2937 Hydrogen 1.32 2 3704 ______________________________________
From Table 1 it can be seen that hot hydrogen has the highest sonic velocity and thus, in theory, would be an optimum gas to serve as the working fluid to achieve the highest velocity for a projectile.
Current propellants produce a mixture of gas made up of various amounts of nitrogen, carbon dioxide, carbon monoxide, water vapor, and hydrogen. Solids produced in gun propellant reactions, such as these produced by black gun powder, have only a slight effect on the properties of the gas because during the rapid expansion involved in accelerating the projectile, the gas phase expands away from the solids and the gas behind the projectile that provides the acceleration is largely free of solids. Table 2 indicates the approximate concentration of the component of the gas phase and the resultant sonic velocity of two current propellants.
TABLE 2 ______________________________________ Solids Mole % Gas Vol Wt Sonic Propellant CO.sub.2 CO N.sub.2 H.sub.2 O H.sub.2 % % Velocity ______________________________________ Black 22.0 44.8 33.2 0 0 .0095 51.2 944 Powder Nitro- 16.3 38.5 12.5 24.4 8.3 0 0 1223 cellulose ______________________________________
From Table 2 it can be seen that nitrocellulose based propellants should provide higher velocities with light projectiles than does black powder. This is consistent with the velocity performance observed in the use of these two propellants.
Ammonium azide, has been known for over seventy years since its preparation by Curtus in 1890. Moreover, it has been employed in a number of environments. For example, Boyer, U.S. Pat. No. 2,981,616, discloses a composition of matter generating gases, which comprises a mixture of an azide, which may be ammonium azide, and an oxidizing compound.
Koch, Jr., U.S. Pat. No. 3,066,479, discloses a method of stabilizing an azide, which may be ammonium azide, and the resulting composition. The azide of this patent is stabilized by providing an excess of the base forming the cation, which, in the case of ammonium azide, is exemplified by anhydrous liquefied ammonia. The resulting azide composition is disclosed as being useful as a fuel gas in rockets, gas turbines or the like.
However, ammonium azide has not heretofore been utilized as a gun propellant either alone or in admixture, however, because it is commonly believed to be highly impact and friction sensitive.
Moreover, although traditional gun propellants are satisfactory for many applications, there remains a need for gun propellants capable of propelling projectiles at higher velocities and greater distances, thereby to inflict greater damage on intended targets.
Accordingly, it is an object of the present invention to provide a new and improved gun propellant.
It is also an object of the invention to provide a method of propelling a projectile, comprising igniting an effective amount of the new and improved propellant described herein, to fire the projectile from a gun at a desired velocity.